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We propose a single observable to witness the nonzero quantum discord of an unknown quantum state provided that we have four copies of the state. The expectation value of this observable provides a necessary and sufficient condition for…

Quantum Physics · Physics 2015-05-27 Chengjie Zhang , Sixia Yu , Qing Chen , C. H. Oh

Coherence of a quantum state intrinsically depends on the choice of the reference basis. A natural question to ask is the following: if we use two or more incompatible reference bases, can~there be some trade-off relation between the…

Quantum Physics · Physics 2016-07-20 Uttam Singh , Arun Kumar Pati , Manabendra Nath Bera

Quantum error correction (QEC) enables reliable computation on noisy hardware by encoding logical information across many physical qubits and periodically measuring parities to detect errors. A decoder is the classical algorithm that uses…

Programming Languages · Computer Science 2026-03-23 Abtin Molavi , Feras Saad , Aws Albarghouthi

Quantifying coherence has received increasing attention, and considerable work has been directed towards finding coherence measures. While various coherence measures have been proposed in theory, an important issue following is how to…

Quantum Physics · Physics 2018-05-02 Da-Jian Zhang , C. L. Liu , Xiao-Dong Yu , D. M. Tong

Quantum tomography is the main method used to assess the quality of quantum information processing devices, but its complexity presents a major obstacle for the characterization of even moderately large systems. The number of experimental…

Quantum Physics · Physics 2015-03-19 Marcus P. da Silva , Olivier Landon-Cardinal , David Poulin

Coherent information quantifies the transmittable quantum information through a channel and is directly linked to the channel's quantum capacity. In a monitored quantum circuit, regarded as a quantum channel, extensive and positive coherent…

Quantum Physics · Physics 2025-12-11 Dongheng Qian , Jing Wang

Quantifying the entanglement and coherence of quantum systems is a topic of significant theoretical and practical interest. In this paper, we propose a method to evaluate lower bounds for several widely used coherence measures and genuine…

Quantum Physics · Physics 2025-08-19 Mingyu Liu , Xian Shi

Entanglement between remote quantum mechanical systems enables a range of quantum information tasks in communication, computation and distributed sensing. Large numbers of entangled subsystems also require experimentally accessible and…

Quantum Physics · Physics 2026-03-23 Kai Ryen Bush , Kjetil Børkje

We report the experimental demonstration of a one-way quantum protocol reliably operating in the presence of decoherence. Information is protected by designing an appropriate decoherence-free subspace for a cluster state resource. We…

Quantum Physics · Physics 2009-11-13 R. Prevedel , M. S. Tame , A. Stefanov , M. Paternostro , M. S. Kim , A. Zeilinger

Purity and coherence of a quantum state are recognized as useful resources for various information processing tasks. In this article, we propose a fidelity based valid measure of purity and coherence monotone and establish a relationship…

Quantum Physics · Physics 2021-04-09 Indrajith V S , R. Muthuganesan , R. Sankaranarayanan

Experimental determination of an unknown quantum state usually requires several incompatible measurements. However, it is also possible to determine the full quantum state from a single, repeated measurement. For this purpose, the quantum…

Quantum Physics · Physics 2008-03-25 Xinhua Peng , Jiangfeng Du , Dieter Suter

Extending the concept of steerability for quantum states, channel steerability is an ability to remotely control the given channel from a coherently extended party. Verification of channel steering can be understood as certifying coherence…

Quantum Physics · Physics 2020-01-29 InU Jeon , Hyunseok Jeong

Certifying that quantum devices behave as intended is crucial for quantum information science. Here, methods are developed for certification of both state preparation devices and measurement devices based on prepare-and-measure experiments…

Quantum Physics · Physics 2020-10-07 Armin Tavakoli

The rigorous resource framework of quantum coherence has been set up recently and excited a wide variety of interests. Here we show that a quantum cavity optomechanical system, as an emerging platform, can behave with a certain value of…

Quantum Physics · Physics 2016-12-21 Qiang Zheng , Jianwei Xu , Yao Yao , Yong Li

We describe a detector that measures the mutual coherence of two optical fields directly using quantum interference, free from photon noise of the individual irradiances. Our approach utilizes Raman transition in an atomic system where the…

Quantum Physics · Physics 2008-12-16 Jungsang Kim , David J. Brady

Dimension witnesses allow one to test the dimension of an unknown physical system in a device-independent manner, that is, without placing assumptions about the functioning of the devices used in the experiment. Here we present simple and…

Quantum Physics · Physics 2013-04-16 Nicolas Brunner , Miguel Navascués , Tamás Vértesi

Quantum instruments derived from composite systems allow greater measurement precision than their classical counterparts due to coherences maintained between N components; spins, atoms or photons. Decoherence that plagues real-world devices…

Quantum Physics · Physics 2014-02-04 Sergey I. Knysh , Edward H. Chen , Gabriel A. Durkin

Recently, the basic concept of quantum coherence (or superposition) has gained a lot of renewed attention, after Baumgratz et al. [PRL 113:140401 (2014)], following \AA{}berg [arXiv:quant-ph/0612146], have proposed a resource theoretic…

Quantum Physics · Physics 2017-08-01 Tanmoy Biswas , María García Díaz , Andreas Winter

Quantum systems, in general, output data that cannot be simulated efficiently by a classical computer, and hence is useful for solving certain mathematical problems and simulating quantum many-body systems. This also implies, unfortunately,…

Quantum Physics · Physics 2017-10-04 Keisuke Fujii , Masahito Hayashi

Quantum coherence -- an indispensable resource for quantum technologies -- is known to be distillable from a noisy form using operations that cannot create it. However, distillation exacts a hidden coherent measurement cost, which has not…

Quantum Physics · Physics 2025-04-16 Varun Narasimhachar